The number 123.45 can be represented as a decimal floating-point number with the integer 12345 as the significand and −2 as the exponent with 10 as the base.

12345 × 10⁻²

This value also can be represented in normalized form

1.2345 as the fractional coefficient, and +2 as the exponent with 10 as the base

1.2345 × 10⁺²

For base 2, this 1.xxxx form is also called a normalized significand.

0.xxxx form is called a normed significand.
0.12345 × 10+3

The IEEE standard used  32-bits to represent
a single precision floating point number


First bit is the sign bit
The sign bit is 0 for positive, 1 for negative numbers

The exponent's is 23 bits long
exponent's value represented in base 2
With 23 bits we can represent maximum 2²³ values

The last 8 bits represent mantessa
It is the fractional part of the number represented in

  11110000 11001100 10101010 10101111  // 32-bit integer
= +1.1110000 11001100 10101011 x 2³¹     // Single-Precision Float
=   11110000 11001100 10101011 00000000  // IEEE 32b sp fp

Check this online number converter
http://www.h-schmidt.net/FloatConverter/IEEE754.html